Crank-shaft.



No. 794,783- PATENTBD JULY 18, 1905. r. .7. com: & w. s. STOT-HOFF.

GRANK SHAFT.

APPLICATION FILED APR: 27. 1905.

2 SHEETS-31321 1.

No. 794,783 I PATENTED JULY 18, 1905.

' F. J. COLE & w. s. STOTHOPF.

CRANK SHAFT. I APPLICATION FILED APB.z 27. 1905.

2 SHEETS-SHEET 2.

FIG 4.

WITNESSES yam mam muasw I:v GRAHAM cu, umocnunzns. WASMI'AGYON. u r;

NITED STATES Patented July 18, 1905.

PATE T OFFicE.

FRANCIS J. COLE AND WILLIAM S. STOTHOFR. OF SOHENEOTADY, NEW YORK, ASSIGNORS TO AMERICAN LOOOMOTIVE COMPANY, OF NEW? YORK, N. Y., A CORPORATION OF YORK.

CRANK-SHAFT.

SPECIFICATION forming part of Letters Patent No. 794,783, dated July 18, 1905.

Application filed April 27, 1905. Serial No. 257,594-

To a whom it may concern:

Be it known that we, FRANCIS J. COLE and WILLIAM S. Srornorr, of Schenectady, in the county of Schenectady and State of New York, have jointly invented a certain new and useful Improvement in Crank-Shafts, of which improvement the following is a specification.

Our invention, while more particularly designed for applicationin crank-axlcs for locomotive-engines, relates generally to crank shafts or axles having two double cranks or pairs of crank-arms fixed thereon at an angle one to the other for connection to two independently reciprocating motor pistons; and its object .is to provide means whereby said crank-arms and their connections may be more effectively counterbalanced than heretofore and the crank-shaft be made .in such form as to be capable of being easily manufactured and the metal thereof be thoroughly worked in pieces of convenient size for handling.

To this end our invention, generally stated, consists in the combination of a shaft or axle, two pairs .of crank-arms fixed thereon at an angle one pair to the other, and a counterbalance fixed on the shaft on the opposite side of its axis from the crank-arms and having its center of gravity in a plane intermediate of and at substantially equal angles to the radial planes of the pairs of crank-arms.

The improvement claimed is hereinafter fully set forth.

In the accompanying drawings, Figure 1 is a view in perspective of a locomotive crankaxle, illustrating an embodiment of our invention; Fig. 2, an end view of the same; Fig. 3, a side view in elevation; Fig. 4, a similar view illustrating a modification of structural detail, and Fig. 5 an end view of the axle of Fig. 4.

Referring first to Figs. 1 to 3, inclusive, in the practice of our invention we provide a shaft or axle 1, which is ordinarily of cylindrical form and is finished at desired distances from its ends so as to provide journals adapted to rotate in suitable bearings in the ordinary manner. Two pairs of crank-arms 2 2 and 3 3, respectively, are formed or fixed upon the shaft 1, the arms of each pair being connected by cylindrical crank-pins A and 5, respectively. The pairs of crank-arms are set upon the shaft with their radial planes (indicated by dotted lines in Figs. 2 and 5) at an angle one to the other, this angle being ordinarily, and as shown in the drawings, one of ninety degrees. The shaft 1 is designed to be rotated by two independently-reeiprocating steam-engine or other motor pistons through connections from the same to the crank-pins 4c and 5, such manner and means of operation being familiar to those skilled in the art and not constituting in and of themselves part of our present invention. The necessity of counterbalancing the crank-arms and the reciprocating parts referred tot'. c., the pistons and their connections--in order to minimize jars and shocks in the rotation of the shaft, has been fully recognized by constructors and has heretofore been sought to be met by the provision of an independent counterbalanceweight for each crank-arm or pair of crankarms, said counterbalance-weights being set substantially diametrically opposite to their respective crank-arms and consisting either of prolongations of said arms or independent members fixed to the shaft with their centers 'of gravity on the opposite side of its axis from the crank-pins, there being consequently either four or two of them, as the case may be, on each shaft having two pairs of crankarms. Under our invention instead of independently counterbalancing each pair of crank-arms, as heretofore, we provide a counterbalance 6, which exerts its action relatively to both pairs of crank-arms 2 2 and 3 3, said counterbalance consisting of an arm which projects from the shaft 1 on the opposite side of its axis from the crank-arms and which is made of proper weight to compensate for the oppositely-acting weight of the crank-arms and of the motor-pistons and their connections and has its center of gravity in a plane (indicated by the dotted lines in Figs. 2 and 5) which is intermediate of and at equal angles to the radial planes of the two pairs of crankarms, these angles being in the instance shown forty-five degrees each. When, as shown in Figs. 1 to 3, inclusive, the adjacent members of the two pairs of crank-arms are set sufficiently close together to permit it, the counterbalance may be, as shown, formed as a continuation of said members, extending on the opposite side of the axis of the shaft and in a different radial plane, as above described. It will, however, be obvious that if the pairs of cranks are located at a substantial distance apart, as is often the case in double-cylinder or cross compound stationary engines, the counterbalance may be formed upon or fixed to, the shaft independently of the cranks at any desired intermediate point.

The increased effectiveness of a counterbalance having the relation to the crank-arms above set forth as compared with the counterbalances of the prior art in planes diametrically opposite the crank-arms will be readily apparent if a line be drawn at right angles to a radial line intersecting the center of gravity of the counterbalance and perpendiculars be drawn to the first stated line intersecting the centers of the crank-pins. These perpendiculars will be materially shorter than the radii of the cranks, and the leverageof the counterbalance will be correspondingly increased for any determined weight, thus enabling its weight and mass to be decreased as compared with the construction heretofore known and used.

Figs. 4 and 5 illustrate a structural modification in which the center of gravity of the counterbalance has the same relation to the radial planes of the pairs of crank-arms as in the instance first described; but the counterbalance is divided into two similar and parallel sections 6 6, each of which is, as in the former case, a continuation of a crank-arm at an angle thereto and which are connected in line axially with the shaft by a cylindrical member 6. This construction will be found more particularly desirable where the crankshaft is of the built-up type or formed of a number of independent and connected pieces,

as is now the general practice. The two crankarms adjacent to the middle of the shaft and the counterbalance-sections integral therewith may be made of forged steel in pieces which in a locomotive crank-axle will finish to about five inches in thickness. These can be very easily manufactured and the irregular shape of the counterbalance-arms be accurately milled out to the desired form, with the advantage that the metal can be thoroughly worked and will be of convenient size for handling.

Among the advantages of our improvement in practical railroad and other high-speed service may be noted that of reduction of the fiber stress of the material by the balancing of the crank-axle by a member within its own structure. The bending moment due to the revolution of an unbalanced crank-axle at high speeds is known to be considerable and in the ordinary form of solid axle at a speed of seventy-five miles perhouris estimated tobe about five thousand three hundred pounds per square inch.

A further feature of advantage of our improvement consists in its neutralization of transverse bending strains by reason of the rotating members being balanced as nearly as practicable to their own planes of rotation.

We claim'as our invention and desire to secure by Letters Patent 1. The combination of a shaft or axle, two pairs of crank-arms thereon at an angle one pair to the other, and a counterbalance projecting from the shaft on the opposite side of its axis from the crankarms, and having its center of gravity in a plane intermediate of, and at substantially equal angles to, the radial planes of the pairs of crank-arms.

2. The combination of a shaft or axle, two pairs of crank-arms thereon at an angle one pair to the other, and a counterbalance composed of acontinuation of the adjacent members of the pairs of crank-arms extending on the opposite side of the axis of the shaft and having its center of gravity in a plane intermediate of, and at substantially equal angles to, the radial planes of the pairs of crankarms.

3. The combination of a shaft or axle, two pairs of crank-arms thereon at an angle one pair to the other, a counterbalance composed of two sections each of which is a continuation of one of the adjacent members of the pairs of crank-arms, extending on the opposite side of the axis of the shaft and having its center of gravity in a plane intermediate of, and at substantially equal angles to, the radial planes of the pairs of crank-arms, and a member connecting the counterbalance-sections in line axially with the shaft.

FRANCIS J. COLE. WILLIAM S. STOTHOFF. Witnesses:

E. H. REESE, A. J. BRAMAN. 

